1. Field of the Invention
The present invention relates to hinge assemblies and, particularly, to an automatic opening hinge assembly for foldable devices such as portable telephones, portable computers, and so on.
2. Discussion of the Related Art
At present, perhaps the most popular portable electronic device in the marketplace is the foldable mobile telephone, which generally includes a cover section and a body section. The cover section and the body section are rotatably interconnected through a hinge assembly, for switching the telephone between an in-use position and a closed position.
One kind of hinge assembly employs a cam and a follower, which makes the cover section fold outward from the body section and then hold in an open position. The hinge assembly typically includes a cam having a concave portion, a follower having a convex portion, a shaft having a fixing end, and a spring. The cam and the follower are placed around the shaft. The spring resists the follower to make the concave portion tightly contact the convex portion. The cam, the follower, the shaft and the spring are received in a housing. A flip cover rotates about a main body of the mobile phone by overcoming the force of the spring, thus making the concave portion rotate about the convex portion. However, a user must open the mobile phone using both hands. This makes the mobile phone awkward to utilize in situations when the user has only one hand free. In addition, the spring resists the follower. Thus, the follower needs to overcome the resisting force from the spring to rotate. This creates high amounts of strain and friction between the spring and the follower and the longevity of the hinge assembly can thus be affected.
Therefore, a new hinge mechanism is desired in order to overcome the above-described shortcoming.